Work table

ABSTRACT

A work table is described, having a frame ( 2 ) which is adjustable especially with respect to its height and for the adjustment of which at least one electric motor ( 4 ) with a control device ( 7 ) is provided. In order to provide simple constructional conditions it is proposed that the control device ( 7 ) which is connected to transducer ( 10 ) for the motor load reverses the direction of rotation of the electric motor ( 4 ) depending on the determined variable and/or change of the motor load and cuts off the same after a thus caused reverse rotation.

FIELD OF THE INVENTION

The invention relates to a work table with a frame which is adjustableespecially with respect to its height and for the adjustment of which atleast one electric motor with a control device is provided.

DESCRIPTION OF THE PRIOR ART

In order to ensure favorable ergonomic conditions in the region of aworkplace, e.g. at a work table for example, it is known to provide worktables with a frame which is adjustable especially with respect to itsheight. In order to simplify said height adjustment of work tables,electric motors are used which can be actuated via a control device. Anelectric drive leads to the likelihood however that on the occurrence ofan obstruction in the region of the adjusting path of the work table, anitem placed on the work table or drive parts, said obstruction will notbe recognized and will be loaded with a force which is relativelyconsiderable as a result of the electromotive drive, leading to anendangerment of the obstruction, as well as the work table or the itemsituated on the work table. This applies in particular when body partsrepresent such obstructions, because in this case there is a relativelyhigh risk of injury.

SUMMARY OF THE INVENTION

The invention is thus based on the object of providing a work table ofthe kind mentioned above in such a way that obstructions which reach thepath of movement of the work table or drive parts are detected in asimple fashion in order to enable the cut-off of the table drive beforecausing any damage or injuries.

This object is achieved by the invention in such a way that the controldevice which is connected to a transducer for the motor load reversesthe direction of rotation of the electric motor depending on thedetermined variable and/or change of the motor load and cuts off thesame after a thus caused reverse rotation.

Since any obstruction reaching into the path of movement of a work tableor its drive parts will increase the motor load, the occurrence of anobstruction can be recognized through a respective monitoring of themotor load, namely independent of the respective local position of theobstruction. For this purpose it is merely necessary to provide atransducer for the load of the motor or motors and to provide a controldevice with the determined motor loads in order to reverse the directionof rotation of the drive and to cut of the motor or motors after arespective return path in the case of the occurrence of a respectivechange in the motor load or on exceeding a predetermined load threshold.The reversal of the drive offers the advantage over the mere cut-off ofthe motors that the obstruction is released again after re-starting themotion and that it can therefore be removed in an unhindered manner fromthe adjusting region of the work table.

The motor load can be determined in different ways, e.g. through theeffective torque which can be detected by means of a pressure sensorprovided in the course of the motor support. Especially simpleconstructional conditions are obtained however when the transducer forthe motor load consists of a measuring device for the motor currentwhich changes with the motor load.

For the purpose of the reverse movement of a work table contrary to thepredetermined table adjustment, simple constructional conditions areobtained for triggering the motor when the control device cuts off theelectric motor after the reversal of the direction of rotation via atimer element which determines the reversal path. The reversal path canbe adjusted to the respective conditions through the adjustability ofsuch a timer element.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter of the invention is shown by way of example in thedrawing, which shows a work table in accordance with the invention in aschematic block diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The illustrated embodiment shows a work table with a table board 1 whichis carried by a frame 2 comprising telescopic legs 3 for the heightadjustment of table board 1. Said telescopic legs 3 are adjustable withthe help of electric motors 4 which drive gearwheels 6 combing a toothedrack 5 when the electric motors 4 are triggered accordingly via acontrol device 7. An input unit 8 is used for the purpose of actuatingthe illustrated actuating device, which input unit can also be inconnection with the control device 7 in a wireless manner and comprisesa conventional input field 9 for operating the work table.

In order to recognize obstructions in the region of the adjusting pathfor the table board 1 or an item placed on the table board 1 and inorder to trigger the electric motors 4 via the control device 7 in sucha way that when approaching the obstruction neither the obstruction northe work table or any device positioned on the table board 1 will bedamaged, the motor load is detected via transducer 10 and is forwardedto the control device 7, so that as a result of the respective changesin the load it is possible to carry out an intervention in the motorcontrol. The configuration is made in such a way that the electricmotors 4 are not only stopped but are also reversed in their directionof rotation in order to revert the table board 1 in order to release theobstruction. For this purpose, following the reversal of the directionof rotation of the electric motors 4, their cut-off is controlled via atimer element 11 which predetermines a preferably adjustable timeinterval for the motor operation in the opposite direction.

The transducers 10 for the motor load are arranged in the respectiveembodiment as measuring devices 12 for the respective motor current andinterposed in the supply lines 13 between the motors 4 and a powersource 14 which can be present in the form of a power unit or a batteryfor example. On the basis of the motor current which changes with themotor load, an effective monitoring for the unhindered adjustment of thework table is obtained, so that in the case of an occurrence of anobstruction the adjustment of the work table as predetermined by theinput device 8 is interrupted and is reversed by an amount which leadsto the release of the obstruction approached by the work table or anitem placed on the table.

1. A work table with a frame (2) which is adjustable especially withrespect to its height and for the adjustment of which at least oneelectric motor (4) with a control device (7) is provided, wherein thecontrol device (7) which is connected to transducer (10) for the motorload reverses the direction of rotation of the electric motor (4)depending on the determined variable and/or change of the motor load andcuts off the same after a thus caused reverse rotation.
 2. A work tableaccording to claim 1, wherein the transducer (10) for the motor loadconsists of a measuring device (12) for the motor current.
 3. A worktable according to claim 1, wherein, the control device (7) cuts off theelectric motor (4) via a timer element (11) after the reversal of thedirection of rotation.